Cathode design

Kazimir, E.S. (1999) Monopolar Cathode Design Improvements and Other Diaphragm Cell Component Advances. ELTECH Systems Corporation, Chlorine/Chlorate Seminar. 

This cathode design, with the stirring described, is regarded as preferable to the combination used by Lukens 3 and much simpler in construction. It provides better dispersion of the organic material, a feature which is particularly necessary if these reductions are carried out in aqueous solution (Note 6). 

On the other hand, the medical condition where the heart beats too fast is known as tachycardia. If untreated, tliis condition may lead to ventricular fibrillation, that is, a condition in which the heart stops beating and shakes uncontrollably and is usually fatal. In 1980, a special device was developed and implanted in patients. It could sense the condition and provide a shock that would stop the fibrillation and restore the normal sinus rhythm via an electrode sutured onto the heart. The device was first powered by a lithium/vanadium pentoxide system later it was replaced by a system using a cathode material of silver vanadium oxide (SVO or Ag2V40ii). This is the actual system used in modem ICDs (implantable cardioverter/defibrillator). Another material used is the lithium/manganese dioxide system. Also, a new system using a sandwich cathode design with an inner cathode material of carbon monofluoride and an external cathode layer of silver vanadium oxide is in wide use. 

The static cylindrical geometry offers a convenient cathode design for small scale operations and has primarily been used for precious metal extraction. Mass transport may be enhanced by the use of tangential manifolds emd the use of a reasonable flow rate. 

Figure 8.12 (a) Schematic of the 4.0 kW ceramic end window X-ray tube, called the Super Sharp Tube , (b) Close up of the window end of the Super Sharp Tube , showing the circular cathode design of this tube. [Courtesy of PANalytical, Inc., The Netherlands (www.panalytical.com).]... 

The step change in pore structure can be fabricated in discrete steps. It also allows the use of dissimilar materials for the porous structure, as used in early Westinghouse SOFC cathode designs and discussed by Thorogood et al. for oxygen transport membranes [12]. 

Because of this, and for obvious economic reasons, there is a continual search for means of lowering the operating temperatures of these cells, from the current temperature regime towards 650°C or lower. This has led to iimovations in thin film, nanostructured and nanotubular cathode design. 

Another approach is to introduce two or more hollow cathodes, each of a single element, into one envelope. This technique also is subject to the problem of selective volatilization but at a lower rate than the single hollow cathode design. 

FIGURE 2.7. Comparison of Hooker and Diamond cathode designs. A finger type construction (Hooker type S cell) B flattened tube-type construction (Columbia-Hooker Diamond, Hooker type T ). 

A unique feature of the cathode design is the extension of the cathode fingers from the back plate, which allows easy inspection of the cathode surfaces, and the adaptability to use synthetic separators with minor modifications. The anolyte compartment is connected to an independent brine feed tank by flanged connections and chlorine leaves from the top, through the brine feed tank and then to the chlorine header. Each electrolyzer is fitted with a level alarm, which monitors the level of all the cells in the unit. Figure 5.16 is an isometric cutaway of a Glanor V Type 1144 electrolyzer. 

Improvements have been made to the anode and cathode design and fabrication techniques, as well as to the gasket and manifold materials. These have resulted in a uniform current distribution across the active membrane area and increased internal circulation. In addition, the use of modular bipolar paks with the use of only eight bolts reduces cell renewal time. 

Since the focus of this paper is on pollution control applications of metal recovery, the complex and as yet incompletely told story of the early development of electroplating, surface finishing and early electrowinning techniques will not be discussed further. The development of electrolytic cells for pollution control applications of metal recovery dates from the mid-1960 s when several major advances in electrochemical engineering took place. Advances in potential and current distribution theory, mass transfer processes, coupled with the introduction of new materials, created a stimulus for the introduction of novel cathode designs with improved mass transfer characteristics. 

Cathode design considerations include the conductivity of the active material its stability relative to various forms of carbon conductors volumetric changes of the reaction products particle size influenced by electrode thicknesses and rate requirements the use of processing aids such as polymers, surfactants, and rheology aids and how the active materials will interface with a current collector. Additionally, in the case of lithium cells, it is critical to conditicm the cathode components prior to cell assembly to remove moisture and volatile process aids which can leach into the organic electrolyte and then react with lithium metal. Such reactions are almost always detrimental to cell impedance and product shelf life. 

The implementation of ECD on ICR cells is nicely compatible with IRMPD. One approach uses a hollow cathode [158] instead of a filament to deliver the electrons. The hollow cathode offers a wider beam enlarging the volume where ECD can occur within the ICR cell. The IR laser then passes through the central hole -a setup that exerts some restrictions to the ICR radii where ions can interact with the laser beam. Several cathode designs are in use (Figs. 9.36 and 9.37) [159]. 

M Company To developed MEA s with improved cathodes, Design and fabrication of MEAs... 

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